Down, down, deeper and down

Materials World magazine
10 Jun 2014

One of the pleasures of reading Materials World each month is the sheer range of invention, ingenuity and endeavour that is reported in the quest for both discovering new materials and mining the ores from which some of our oldest metals are extracted. I have read about plans to extract mineral ores from some of the most inhospitable places on Earth, and beyond, but I hadn’t realised that human endeavour has reached a place some consider to be even more remote than outer space. That was until I attended a fascinating Mining Institute of Scotland talk by Professor Dorrik Stow of Heriot Watt University, entitled Mining the Deep Ocean.

In some ways we know more about deep space than the deep ocean trenches that mark the boundaries where the submarine tectonic plates slowly grind across Earth’s mantle. Most of what we know comes from physically sending down remotely operated vehicles to have a look, which is both expensive and restricted by limited coverage. What we do know is that hydrothermal vents, first discovered along the Galapagos Rift in 1977, have been observed in several locations where tectonic plates meet. Dissolved within the superheated salt water emerging from these vents are sulphides of copper, zinc, silver and gold, which precipitate on contact with the cold seawater at ocean floor to create vast swathes of mineral deposits.

A combination of remote underwater technology developed for the oil and gas industry together with rising demand, and prices, for these metals mean that plans to recover the mineral deposits from the deep ocean have moved significantly closer to becoming reality. Canadian mining company Nautilus Minerals has recently finalised an agreement with Papua New Guinea to extract copper, gold and other valuable metals from a depth of 1,500m, and has even constructed a 310-tonne underwater bulk cutter to break up these deposits and pump the slurry to surface.

So it is clearly technically feasible, and with Nautilus reporting an indicated mineral resource of 7.2% copper, 5.0g/t gold, 23g/t silver and 0.4% zinc, it is a potential yield much better than most land deposits. But is it economic to recover? The same thing was asked about offshore oil and gas production 30 years ago, but today we are extracting that from waters deeper than 1,500m, so who is to say the same will not happen in this instance? Like so many of the features in Materials World, opinion will be divided on whether it is an engineering marvel or an environmental catastrophe.

Personally, I can’t help wondering if the time has come to make better use of what we already have, through reuse, recycling and using less in the first place. Exploration of the ocean floor has revealed extraordinary animals as well as these minerals, and there are certainly more yet to be discovered. Are we in danger of causing their extinction without ever knowing they existed?